This invention relates to a development unit for electrophotocopiers, comprising a magnetic brush in which a rotatable sleeve of non-magnetic material encloses a plurality of magnets fixed on to a rotatable shaft, and a toner container situated adjacent to the sleeve in order to feed the magnetic brush through a slit with the toner free from any lumps or foreign bodies.
Various types of magnetic brush development units are known in which the toner, contained in a container adjacent to the magnetic brush, is fed to the magnetic brush after being freed of any lumps of toner by mechanical agitation and crushing devices.
In one such development unit, the agitation devices are formed from a magnetic element rotatable in the toner container in proximity to the feed slit. By virtue of the rotation of the magnetic element, the toner is kept in continuous agitation so that the possibility of lump formation is reduced, and any previously existing lumps are broken up.
In another type of development unit, the agitation device is constituted by a rigid bar located on the container, and moved in a reciprocating manner by a rotating cam rigid with the shaft of the magnetic brush in order to agitate the toner and prevent lump formation.
All these devices are mechanically complicated and easily subject to faults. Moreover, they do not prevent the formation of lumps in the feed slit, which form by accumulation and compacting of the toner, especially during long periods of inactivity of the copier.